Nov. 10, 2010 -- New research finds no link between high cholesterol in midlife and Alzheimer's disease in old age.

Scientists followed a group of Swedish women for three decades -- from middle age to old age -- and found no increase in Alzheimer's risk among women whose cholesterol was high in their 40s, 50s, and 60s.

The finding appears to contradict several earlier studies, which did suggest a role for elevated midlife cholesterol in the development of late-life dementia.

But many of those studies only included people who survived long enough to develop Alzheimer's disease, which could have influenced the outcomes, says researcher Michelle M. Mielke, PhD, who is an assistant professor of psychiatry at Baltimore's Johns Hopkins University School of Medicine.

"Because we followed people from middle age, we were able to look at the predictive value of cholesterol levels for developing dementia," she tells WebMD.

Alzheimer's and Cholesterol

The study included 1,462 women, most of whom were in their 40s and 50s at enrollment.

All the women had physical exams and completed lifestyle surveys when they entered the study and at various times later on. Neuropsychiatric exams were performed over the 32 years of follow-up. Women who survived to age 70 also underwent more extensive periodic testing for dementia.

During 32 years of follow-up, 161 women developed dementia.

The researchers concluded that cholesterol levels measured in middle age did not predict progression to Alzheimer's disease later in life.

But a link was seen between rapidly declining cholesterol levels in the elderly and dementia.

Women whose cholesterol decreased the most from middle age to old age were more than twice as likely to develop dementia as women whose cholesterol levels increased or stayed the same.

Mielke says rapidly declining cholesterol late in life appears to be associated with increased frailty and may be an early sign of dementia.

"Around 10 years before people develop symptoms of dementia they tend to become more frail," she says. "They may be forgetting to eat and start to lose weight, which can impact cholesterol levels."

Managing Cardio Risk Still Important

A major goal of Alzheimer's prevention research is to identify modifiable risk factors for late-life dementia.

Although the study found no evidence that elevated midlife cholesterol predicts Alzheimer's disease, managing high cholesterol and other cardiovascular risk factors in middle age could still be an effective strategy for lowering risk, experts tell WebMD.

"There is still good reason to be concerned about cardiovascular disease in relation to Alzheimer's risk," says Stanford University Medical Center professor of neurology and epidemiology Victor Henderson, MD. "In the absence of stronger data, I think it still makes a lot of sense to pay careful attention to managing cardiovascular risk."

"There are plenty of good reasons to keep cholesterol at appropriate ranges, and lowering Alzheimer's risk may still be one of them," he tells WebMD.

Mary Haan, DrPH, says it is now clear interventions for preventing dementia are likely to be most effective many decades before mental decline becomes evident.

"You can't really hope to prevent dementia in an 80-year-old who already has symptoms," she tells WebMD. "But we may have an impact in much younger people and there is evidence that vascular risk factors in midlife impact dementia and Alzheimer's risk."